You need to build it yourself, but this YM2151 tracker for OSX seems to be coming along nicely.

Did a whole fuckton of stuff. Added a player (plays the tracks without the UI), added PatchGen (generates patches from a website), and did a fuckton of stuff to the tracker, including: Adding effects, making Volume controls work. Now you should _really_ be able to make great music. All patches and tracks since the big change should still work. I also redid all the patches, and added some drums patches.

via SquidMan’s herzeleid at master – GitHub.

UPDATE

EDIT: Also, since my hosting changed, the old link to the documentation is gone. The location that should be used is